Balance

ABSTRACT

A single-pan analytical balance having two beams mounted spacedly one above the other in main bearings whose normally horizontal axes perpendicularly intersect each other. One arm of each beam carries a counterpoise whereas the other arm is secured to a hanger assembly carrying a top-loading weighing pan by hanger bearings whose pivot axes are parallel to the corresponding main bearings. The bearings consist essentially of flexible metal ribbons. An electromagnetic device acting on the hanger assembly permits weighing by compensation in a known manner.

United States Patent [1 1 Kupper' 11] 3,734,218 [4 1 May 22, 1973 [s41BALANCE [75] Inventor: Walter Kupper, 8606 Greifensee,

Switzerland [73] Assignee: Mettler Instrument AG, Greifensee,

Switzerland [22] Filed: Sept. 25, 1972 [21] Appl. No.: 291,750

[30] Foreign Application Priority Data Dec. 21, 1971 Switzerland..18608/71 [52] US. Cl. ..177/203, 177/212, 177/255, 177/DIG. 9

[51] Int. Cl G0lg l/34, GOlg 7/00, GOlg 21/24 [58] Field of Search..177/203, 212, 229, 177/246, 252, 255, D16. 9

[56] References Cited UNlTED STATES PATENTS Ast "177/255 x 3,347,32810/1967 Schieser et al. 177/229 3,443,653 5/1969 Marshall ..177/229 XFOREIGN PATENTS OR APPLICATIONS 984,400 2/ 1965 Great Britain ..177/255Primary Examiner-George H. Miller, Jr. Attorney-Kurt Kelman et a1.

[57] ABSTRACT A single-pan analytical balance having two beams mountedspacedly one above the other in main bearings whose normally horizontalaxes perpendicularly intersect each other. One arm of each beam carriesa counterpoise whereas the other arm is secured to a hanger assemblycarrying a top-loading weighing pan by hanger bearings whose pivot axesare parallel to the corresponding main bearings. The bearings consistessentially of flexible metal ribbons. An electromagnetic device actingon the hanger assembly permits weighing by compensation in a knownmanner.

9 Claims, 5 Drawing Figures BALANCE This invention relates to balances,and particularly to single-pan analytical balances in which the weighingpan is suspended from a balance beam by means of a hanger, and itsweight and that of the hanger are normally balanced by a counterpoise onthe beam.

Balances of the afore-described type have been built heretofore to highstandards of precision and sensitivity and have found wide acceptancefor chemical analysis work. The hanger of a balance of the known typedepend from the balance beam, and the weighing pan is attached to thelower end of the hanger. The hanger is mounted on the beam by means of aknife edge and plate or another bearing type which permits swingingmovement of the pan. It is common practice to equip such a balance witha damping device which quickly attenuates oscillation of the pan. Still,the time lost by an initial departure of the hanger assembly from aposition in which its center of gravity is not vertically aligned withthe pivot axis of the hanger bearing reduces the number of weighingsthat can be performed in a given time.

It is known to avoid pendulum movement of a weighing pan by mounting thepan on a parallelogram linkage one arm of which is formed by the balancebeam. Balances so equipped are usually top-loading and will be referredto hereinafter as precision balances. They can be operated much fasterthan the afore-described analytical balances and are simpler in theirstructure and operation since they require neither arrestments nordamping devices. Because of certain inherent features, balances of thelast-mentioned type could not heretofore match the precision andsensitivity of the first-described analytical balances.

When a precision balance is equpped with knife-edge bearings, theweighing pan must be offset relative to the bearing which connects thepan carrier in the parallelogram linkage with the balance beam so thatthe horizontal forces resulting from the torque provide compressive ortensional forces which safely secure the link of the parallelogramparallel to the balance beam in its bearings. The bearing plates must beV-shaped in order to prevent shifting of the pivot axes regardless ofthe horizontal forces applied. This causes friction in the bearing andhysteresis effects.

These difficulties can be overcome at least in part by the provision ofbearings consisting of flexible ribbons arranged in two perpendicularplanes which intersect each other in the pivot axis of the bearing. In aprecision balance equipped with such bearings, the weighing pan can bemounted vertically above the bearing connecting the pan carrier with thebalance beam. Still, such a balance is sensitive to off-center loadingof the weighing pan which is practically unavoidable and generates atorque causing some horizontal stress. Additionally, the known balancesemploying bearings of intersecting ribbons tend to develop internalstresses due to minor misalignments which unfavorably affect theaccuracy of the weighings.

If the weight is read'from the angle of inclination of the balance beam,it is very difficult for a balance with parallelogram linkage suspensionto maintain adequate sensitivity over the entire range of angular beammovement.

For these and other reasons, the best precision balances knownheretofore have a sensitivity not exceeding about 1:10 (1 mg in 100 g)whereas other wise equivalent analytical balances have a sensitivity of1:10 or better.

It is the primary object of this invention to provide a balance whichcombines the advantages of the known analystical and precision balanceswhile avoiding the afore-described shortcomings of both.

More specifically, the invention aims at providing a balance in whichthe weighing pan is guided firmly as by the parallelogram linkage of aprecision balance, yet has no inherent features which would prevent itfrom being built to a precision significantly better than 1:10

With these and other objects in view, the invention provides a balancehaving two balance beams mounted on a normally stationary support forangular movement about respective pivot axes. Two counterpoises arerespectively mounted on the beams for angular movement therewith. Ahanger assembly carrying the weighing pan is pivotally secured to afirst one of the balance beams for angular movement about a third pivotaxis and to the second balance beam for angular movement about a fourthpivot axis. All pivot axes extend hoizontally in the operating positionof the balance, and the fourth pivot axis intersects a vertical planeincluding the third pivot axis, preferably perpendicularly.

Other features, additional objects, and many of the attendant advantagesof this invention will readily become apparent as the invention becomesbetter understood by reference to the following detailed description ofpreferred embodiments when considered in connection with the appendeddrawing in which:

FIG. 1 shows a balance of the invention in a perspective view;

FIG. 2 illustrates a portion of the apparatus of FIG. 1 on a largerscale;

FIG. 3 shows a modified detail for the balance of FIG. 1 in aperspective view on a somewhat larger scale;

FIG. 4 diagrammatically illustrates relationships of pivot axesassociated with one of the beams of the balance of FIG. 1; and

FIG. 5 shows a modified bearing arrangement suitable for the balances ofboth FIGS. 1 and 3.

Referring now to the drawing in detail, and initially to FIG. 1, thereis seen a balance whose stationary support structure consistsessentially of a base plate 6 and of two pairs 7,7 and 8,8 of uprightcolumns. The balance has two beams 10,12 arranged spacedly one above theother. A cross bar 28 integrally attached to the center portion of thebeam 10 is mounted between the free upper ends of the columns 7,7 bymeans of main bearings 9,9. A corresponding cross bar 28' of the lowerbeam 12 is similarly mounted by main bearings 11,11 on the upper ends ofthe columns 8,8 which are shorter than the columns 7,7.

In the illustrated equilibrium condition of the balance, the beams 10,12are parallel and horizontal. The bearings 9,9 have a common first pivotaxis which is horizontal in all operating positions of the balance, andthe common second pivot axis of the bearings 11,11 is also horizontaland perpendicular to the vertical plane which includes the pivot axis ofthe bearings 9.9.

The arms of the beams 10,12 which extend to the right, as viewed in FIG.1, from the cross bars 28,28 carry respective counterpoises 13,14 whichmay be adjusted along the beams and fixed in the adjusted positions asis conventional and has not been illustrated. A

hanger assembly 15 is supported on the other arms of the two beams10,12.

Cross-bars 34,34 on the ends of the beams 10,12 remote fromcounterpoises 13,14 are parallel to the cross arms 28,28 on the samebeam and are pivotally connected with the four corners of a squarebottom plate 16 diagonally braced by a cross-shaped rib 17. Three rigidupright bars 18 extend from the bottom plate 16 beyond the upper balancebeam and hold a weighing pan 19 parallel to the bottom plate 16.

The bottom plate 16 is suspended from the cross bars 34,34 by respectivepairs of pivots 21,21 and 20,20.

Each pivot 21,21 includes a flexible ribbon assembly 22 attached to thecross bar 34 and, a rigid connector strip 23 depending from the ribbonassembly 22 and twisted about its longitudinal axis in such a mannerthat its lower transverse edge is located in a vertical planeperpendicular to the vertical plane drawn through the uppertransverseedge which is attached to the ribbon assembly 22. An additional flexibleribbon assembly 22' of each pivot 21,21 is attached to the lowertransverse edge of the connector strip 23. The pivots 21,21 permit thehanger assembly to move angularly about a third horizontal pivot axisthrough the ribbon assemblies 22, the third axis being parallel to thecross bar 34, and such movement would be analogous to the pendulummovement of the hanger and pan on a conventional analytical balance.

The pivots 20, consist of respective single flexible ribbon assemblieswhich prevent the afore-described pendulum movements about the thirdpivot axis, but would permit oscillation about a fourth pivot axisparallel to the beam 34' in the absence of the pivots 21, 21. The fourpivots jointly guide the bottom plate 16 and the pan 19 in the samemanner as a parallelogram linkage in that they hold the supporting faceof the pan 19 in a horizontal position at all times while the hangerassembly 15 as a whole moves vertically up or down.

The balance is held in the illustrated position by an electromagneticcompensating mechanism 24, known in itself, which consists essentiallyof a permanent pot magnet 25 and a movable coil, obscured by the magnet25, and suspended from the bottom plate 16 by a carrier bar 26. Themagnet 25 is fixedly mounted on the base plate 6 and supplements theforces of the counterposies in accordance with the current passingthrough the movable coil in a manner known in itself, for example, fromthe Swiss Pat. No. 508,204.

The several flexible ribbon assemblies are closely similar or identicalin structure, and only the ribbon assembly constituting the main bearing9 will be described in detail with reference to FIG. 2. One of the twolongitudinal end portions of a rectangular metal ribbon 27, a fewhundreds of a millimeter thick, is clamped by a small plate 29 andscrews 31 to one end of the cross bar 28, while the other end issimilarly clamped by a plate 29' to the rectangularly offset top end ofthe column 7. TI-Ie ribbon 27 is held in a vertical plane in the normaloperating position of the balance by the weight of the cross bar 28 andof associated structure which holds the ribbon 27 under tensile stressand opposes flexing of the ribbon. As will be evident from inspection ofFIG. 1, the lower end portion of each illustrated flexible ribbon isattached to a load whose weight is transmitted by the upper end of theribbon to the stationary balance structure either directly orindirectly. The exposed portion of each ribbon 27 bottom plate 16. Ifthe secondary ribbon assemblies 22" between the clamping plates 29,29has a length of only a few millimeters, and can be flexed only about ahorizontal flexing or pivot axis. Each ribbon 27 is biased by theapplied load toward a vertical plane which includes the associated pivotaxis or flexing axis.

The two ribbon assemblies 22' at the lower ends of the two connectorstrips 23 have ribbons located in parallel vertical planes perpendicularto the common vertical plane defined by the ribbons in the assemblies 22and including the (third) pivot axis of the pivots 22.

The connector strips 23 are necessary for bridging the vertical distancebetween the cross bar 34 and the were not provided, minimal differencesin the lengths of the two strips 23 would cause stresses in the hangerassembly 15 and a concomitant loss in precision and sensitivity. Theflexing axes of the ribbons in the ribbon assemblies 22' are parallel tothe pivot axes of the pivots 20,20, and perpendicular to a verticalplane through the pivot axis of the assemblies 22. Any slight differencein the effective lengths of the strips 23,23 can thus be compensated bya corresponding minimal flexing of the ribbon assemblies 22, therebyavoiding stresses from being developed in the hanger assembly.

This expedient is fully effective only in a compensation type balance inwhich the weighing pan is in the same horizontal plane in all positionsof balance equilibrium, regardless of the load that is being weighed.Such a compensation type balance has been illustrated in FIG. 1. It isnot effective in a balance in which the inclination of the balance beamprovides indicia of the weight to be determined, as will be discussedhereinbelow with reference to FIG. 3.

The minimal angular deviations of the beams 10, 12 during weighing areabsorbed by the flexible ribbons in the pivots 20, 22 without affectingthe sensitivity of the balance.

The balance illustrated partly in FIG. 3 may be identical with thatillustrated in FIG. 1 as far as not illustrated except for aconventional scale and indicia for showing the inclination of one of thebalance beams 10, 12 as a measure of the weight carried by the pan 19.As is seen from FIG. 3, the illustrated balance does not have a magneticcompensation system, and the suspension assembly illustrated in FIG. 3moves vertically between a zero equilibrium position and an equilibriumposition under load. Provisions have to be made, therefore, forpermitting the relative movement of the balance beams and the hangerassembly.

The bottom plate 16 of the hanger assembly is suspended from the twocross bars 34, 34' of the balance beams 10, 12 by means of respectiverectangular frames 32, 33. The frame 32 is attached to the cross bar 34by means of two ribbon assemblies 22a at the respective ends of thecross,bar, and to the bottom plate 16 by another pair of ribbonassemblies 22b located below the two ribbon assemblies 22a respectively.Similarly, the frame 33, partly broken away in FIG. 3 for the sake ofclarity is attached to the cross bar 34' by a pair of upper ribbonassemblies 20a, and to the bottom plate 16 by a pair of ribbonassemblies 20b. Each frame 32,33 is normally vertical, the pivot axes orflexing axes of the associated four ribbon assemblies are parallel, andthe flexible metal ribbons in the four assemblies extend in acommonvertical plane. The frames 32,33 are rigid enough not to besubject to any distortion under the forces exerted on them duringweighing.

When the beams 10,12 are pivoted out of their normal position by a loadapplied to the weighing pan, omitted from FIG. 3, the frames 32,33 aremoved into slightly oblique planes and the associated metal ribbons areshifted out of the common vertical plane. Because of the stiffness ofthe frames, however, the base plate 16 remains precisely horizontal atall times, and the entire hanger assembly moves as if it were guided bya parallelogram linkage.

Similar results can be obtained without the frame 33 if the spacing ofthe bottom plate 16 from the lower beam 12 and the dimensions of theconnecting pivot assemblies are carefully selected.

FIG. 4 diagrammatically illustrates the spatial relationship between thelongitudinal axis of the beam 12, the second pivot axis between thepivots 11,11 and the fourth pivot axis between the pivots 20,20 in fullydrawn lines. The two pivot axes should be as precisely parallel aspossible for highest sensitivity and precision of the balance.Manufacturing tolerances, however, are unavoidable and may cause thepivot axes to deviate from the desired relationship as indicated bybroken lines in a grossly exaggerated manner for the purpose ofconvenient description. The second pivot axis 11-11 may be deflected bysuch tolerances in a horizontal plane while the axis 20-20 may bedeflected vertically, as indicated by short arrows.

Deviations of each pivot axis in a horizon al or vertical direction maybe compensated for in t e manner illustrated in FIG. 5 with reference tothe pivot 20. The cross bar 34a at the end of the beam 12, not itselfshown, differs from the cross beam 34, as illustrated in FIG. 1, inhaving a forked free end. Its two branches 37,39 are separated by a slot36. A metal ribbon 27 of the pivot 20 is attached to the heavier branch39 by a plate 29 and screws 31 as described with reference to FIG. 2.The narrower branch 37 is integral with a rigid strut 35, only partlyshown, which is fixedly fastened to the beam 12. A screw 40 passesfreely through a bore of the branch 39 and threadedly engages a blindbore in the bight portion 38 of the V-shape jointly formed by thebranch37 and the strut 35. When the screw 40 is tightened, the branch 39 isflexed toward the strut 35 in a horizontal plane, and the position ofthe pivot 20 and of the associated fourth pivot axis is shiftedaccordingly to correct a minor and sometimes unavoidable manufacturingdefect.

It is preferred to equip each pair of pivots 9,9; 11,11; 20,20; 21,21with a device of the type shown in FIG. 5. The balance of FIG. 1 when soequipped, can be adjusted by means of the several screws 40 to bepractically unaffected by an off-center position of a load on theweighing pan 19. In inclination balances,- such as the balance partlyshown in FIG. 3, it is preferable additionally to provide analogousdevices for adjusting the parallel alignment of the pivot axes on eachbeam in a vertical direction, the slot 36 and strut 35 in the verticaladjustment devices being offset 90 from the respective positions shownin FIG. 5.

When a series of balances of the invention having the same nominalstructure are built, the necessary number of turns of the adjustingscrews 40 may be determined for one balance of the series by placing astandard weight off-center on the weighing pan and adjusting the screwsuntil the indicated weight is equal to the known weight of the standard.All balances of the same series will then be properly adjusted when thesame number of turns is given to the respective screws 40 for the samedifference between the indicated and known weight of the standard.

While the invention has been described with reference to top-loadingbalances, the weighing pan may be fixedly suspended below the hangerassembly by bars analogous to the bars 18 or similar rigid elementswithout changing the mode of operation and without loss of advantages.The top-loading balance of FIG. 1 is preferably enclosed in a housingwhich protects it against the movement of the ambient air as iscustomary in analytical balances and has not been shown.

The weight compensating system illustrated in FIG. 1, which acts on thearm of each balance beam remote from the associated counterpoise, is notaffected by changes in ambient temperature. The range of the balance maybe enlarged by supplemental weights releasably attached to thecounterpoises in a conventional manner.

The illustrated arrangement in which the pivot axes 20,20 and 21,21 areperpendicular to each other are preferred, but the advantages of theinvention are available by any arrangement in which the two pivot axesintersect each other at an angle significantly greater than 0. Aperpendicular arrangement of the axes permits particularly easyadjustment as shown, for example, in FIG. 5.

The two balance beans 10,12 may be mounted on the common supportingstructure in any desired spatial arrangement. It is preferred, however,to mount them one above the other in the interest of a compact design.The overall height may thereby be reduced to less than that of anotherwise comparable, conventional precision balance having knife edgebearings, in which the overall height cannot be reduced to a value inwhich the parallelogram linkage would become ineffective.

The flexible ribbon pivots illustrated do not oppose flexing withsignificant forces of reaction which could cause inaccurate weighings.THey do not require arrestments, and are mechanically very rugged.Still, at leas some of the advantages of the invention may be achievedin balances having some knife-edge bearings.

It should be understood, therefore, that the foregoing disclosurerelates only to preferred embodiments of the invention and that it isintended to cover all changes and modifications in the examples of theinvention herein chosen for the purpose of the disclosure which do notconstitute departures from the spirit and scope of the appended claims.

What is claimed is:

1. A balance comprising, in combination:

a. normally stationary support;

b. a first balance beam mounted on said support for angualr movementabout a first pivot axis;

c. a second balance beam mounted on said support for angular movementabout a second pivot axis;

d. two counterpoises respectively mounted on said first and secondbalance beams for angular movement therewith;

e. hanger means pivotally secured to said first balance beam for angularmovement about a third pivot axis,

1. said hanger means being secured to said second balance beam forangular movement about a fourth pivot axis,

2. each of said pivot axes extending horizontally in the operatingposition of said balance,

3. said fourth pivot axis intersecting a vertical plane including saidthird pivot axis in said operating position; and

f. a weighing pan fixedly mounted on said hanger means. 2. A balance asset forth in claim 1, wherein said first and third pivot axes spacedlyextend in a common direction, and said second and fourth pivot axesspacedly extend in a common direction.

3. A balance as set forth in claim 2, wherein said fourth axisperpendicularly intersects said vertical plane.

4. A balance as set forth in claim 2, wherein said beams are arrangedone above the other in said operating position.

5. A balance as set forth in claim 2, wherein each balance beam has afirst arm and a second arm, the respective first arms of said balancebeams carrying said counterpoises, and the respective second armsbeingpivotally secured to said hanger means, said balance further includingelectromagnetic compensating means connected to the respective secondarms of said balance beams for adjustably compensating the forcesexerted on said balance beams until said balance beams are stationaryrelative to said first and second pivot axes respectively.

6. A balance as set forth in claim 2, wherein said balance beams eachinclude two cross bar portions, the balance further comprising firstpivot means including two pivot assemblies spaced along a first one ofthe cross bar portions of said first balance beam in the direction ofsaid first pivot axis and connecting said first balance beam to saidsupport, second pivot means including two pivot assemblies spaced alonga first one of the cross bar portions of said second balance beam in thedirection of said second pivot axis and connecting said second balancebeam to said support, third pivot means including two pivot assembliesspaced along the second cross bar portion of said first balance beam inthe direction of said third pivot axis and connecting said first balancebeam to said hanger means, and fourth pivot means including two pivotassemblies spaced along the second cross bar portion of said secondbalance beam in the direction of said fourth pivot axis and connectingsaid second balance beam to said hanger means, said hanger meansincluding a rigid hanger assembly pivotally secured to said balancebeams by said third and fourth pivot means, and rigidly connected tosaid weighing pan, each pivot assembly including a flexible ribbonmember mounted for flexing movement about the associated pivot axis andunder tension opposing said flexing movement, the ribbon members in eachpivot means jointly constituting the sole connecting means respectivelyconnecting said balance beams to said support and to said hanger means.

7. A balance as set forth in claim 2, further comprising first andsecond pivot means respectively securing said balance beams to saidsupport for angular movement about said first and second pivot axes, andthird and fourth pivot means respectively securing said hanger means tosaid first and second balance beams for angualr movement about saidthird and fourth pivot axes, each pivot means including at least oneflexible ribbon member attached to an associated balance beam, saidribbon member being stressed in tension while transmitting the weight ofsaid hanger means and of said weighing pan between said balance beamsand, respectively, said hanger means and said support.

8. A balance as set forth in claim 7, wherein said third pivot meansincludes another flexible ribbon member attached to said hanger meansfor flexing movement about a flexing axis, and rigid weight transmittingmeans connecting said one ribbon member of said third pivot means tosaid other ribbon member for transmitting the weight of said pan and ofsaid hanger means from said other ribbon member to said one ribbonmember and there-by to said first balance beam, said flexing axis andsaid third pivot axis extending in respective perpendicularly offsetvertical planes in said operating position-of the balance.

9. A balance as set forth in claim 7, wherein said second balance beamhas a resiliently deformable portion, one of said ribbon members of saidsecond and fourth pivot means being attached to said deformable portionfor flexing movement about the corresponding pivot axis, said balancefurther including adjusting means for deforming said portiontransversely of said corresponding pivot axis, and for thereby angularlyshifting said corresponding axis.

1. A balance comprising, in combination: a. normally stationary support;b. a first balance beam mounted on said support for angualr movementabout a first pivot axis; c. a second balance beam mounted on saidsupport for angular movement about a second pivot axis; d. twocounterpoises respectively mounted on said first and second balancebeams for angular movement therewith; e. hanger means pivotally securedto said first balance beam for angular movement about a third pivotaxis,
 1. said hanger means being secured to said second balance beam forangular movement about a fourth pivot axis,
 2. each of said pivot axesextending horizontally in the operating position of said balance, 3.said fourth pivot axis intersecting a vertical plane including saidthird pivot axis in said operating position; and f. a weighing panfixedly mounted on said hanger means.
 2. each of said pivot axesextending horizontally in the operating position of said balance,
 2. Abalance as set forth in claim 1, wherein said first and third pivot axesspacedly extend in a common direction, and said second and fourth pivotaxes spacedly extend in a common direction.
 3. A balance as set forth inclaim 2, wherein said fourth axis perpendicularly intersects saidvertical plane.
 3. said fourth pivot axis intersecting a vertical planeincluding said third pivot axis in said operating position; and f. aweighing pan fixedly mounted on said hanger means.
 4. A balance as setforth in claim 2, wherein said beams are arranged one above the other insaid operating position.
 5. A balance as set forth in claim 2, whereineach balance beam has a first arm and a second arm, the respective firstarms of said balance beams carrying said counterpoises, and therespective second arms being pivotally secured to said hanger means,said balance further including electromagnetic compensating meansconnected to the respective second arms of said balance beams foradjustably compensating the forces exerted on said balance beams untilsaid balance beams are stationary relative to said first and secondpivot axes respectively.
 6. A balance as set forth in claim 2, whereinsaid balance beams each include two cross bar portions, the balancefurther comprising first pivot means including two pivot assembliesspaced along a first one of the cross bar portions of said first balancebeam in the direction of said first pivot axis and connecting said firstbalance beam to said support, second pivot means including two pivotassemblies spaced along a first one of the cross bar portions of saidsecond balance beam in the direction of said second pivot axis andconnecting said second balance beam to said support, third pivot meansincluding two pivot assemblies spaced along the second cross bar portionof said first balance beam in the direction of said third pivot axis andconnecting said first balance beam to said hanger means, and fourtHpivot means including two pivot assemblies spaced along the second crossbar portion of said second balance beam in the direction of said fourthpivot axis and connecting said second balance beam to said hanger means,said hanger means including a rigid hanger assembly pivotally secured tosaid balance beams by said third and fourth pivot means, and rigidlyconnected to said weighing pan, each pivot assembly including a flexibleribbon member mounted for flexing movement about the associated pivotaxis and under tension opposing said flexing movement, the ribbonmembers in each pivot means jointly constituting the sole connectingmeans respectively connecting said balance beams to said support and tosaid hanger means.
 7. A balance as set forth in claim 2, furthercomprising first and second pivot means respectively securing saidbalance beams to said support for angular movement about said first andsecond pivot axes, and third and fourth pivot means respectivelysecuring said hanger means to said first and second balance beams forangualr movement about said third and fourth pivot axes, each pivotmeans including at least one flexible ribbon member attached to anassociated balance beam, said ribbon member being stressed in tensionwhile transmitting the weight of said hanger means and of said weighingpan between said balance beams and, respectively, said hanger means andsaid support.
 8. A balance as set forth in claim 7, wherein said thirdpivot means includes another flexible ribbon member attached to saidhanger means for flexing movement about a flexing axis, and rigid weighttransmitting means connecting said one ribbon member of said third pivotmeans to said other ribbon member for transmitting the weight of saidpan and of said hanger means from said other ribbon member to said oneribbon member and there-by to said first balance beam, said flexing axisand said third pivot axis extending in respective perpendicularly offsetvertical planes in said operating position of the balance.
 9. A balanceas set forth in claim 7, wherein said second balance beam has aresiliently deformable portion, one of said ribbon members of saidsecond and fourth pivot means being attached to said deformable portionfor flexing movement about the corresponding pivot axis, said balancefurther including adjusting means for deforming said portiontransversely of said corresponding pivot axis, and for thereby angularlyshifting said corresponding axis.